Author: James Robertson
Date: 00:31:21 08/08/00
Go up one level in this thread
On August 08, 2000 at 03:06:48, Andrew Dados wrote:
>On August 08, 2000 at 02:34:54, James Robertson wrote:
>
>>On August 08, 2000 at 01:54:48, Andrew Dados wrote:
>>
>>>On August 08, 2000 at 00:25:06, James Robertson wrote:
>>>
>>>>I am trying to measure clock cycles for certain functions in my program. Could
>>>>sombodey please explain how to do this? Totally simple methods are preferred. :)
>>>>
>>>>Thanks!
>>>>James
>>>
>>>All modern CPUs starting with Pentium and K2 have TSC 64 bit counter which gets
>>>incremented by 1 for each CPU clock.
>>>Under protected mode reading from this counter is by default disabled, but for
>>>some reason any task can enable instruction for reading TSC.
>>>
>>>(I'll be quoting asm code I wrote before some instructions were supplied by C
>>>inline asm, so in some cases I had to define instructions myself)
>>>
>>>enabling TSC:
>>>
>>>asm
>>
>>Thanks, this looks cool. Unfortunately, I don't know how to interpret the db
>>instructions... how can I use them in VC++?
>>
>>James
>>
>>
>>>db $0f, $20, $c0 {mov eax,cr4}
>>>or eax,32 {Enable TSC}
>>>db $0f, $22, $e0 {mov cr4,eax}
>>>end;
>>>
>>>reading tsc:
>>>
>>>asm
>>>db $0f, $31 {RDTSC : 64bit unsigned tick count goes to eax:edx}
>>>end;
>>>
>>>So writing mini-profiler got really easy with RDTSC.
>>>One remark: TSC is a global counter, not task-related.
>>>
>>>-Andrew-
>
>db srands for 'define byte' and is standard asm directive...
>Look up eg crafty source for how to write procedures in assembler and readable
>by C compilers.
I've written a large amount of assembler.
The compiler chokes on the arguments, not the db statement itself. :(
James
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